require 'openssl'
require 'rest-core/event'
require 'rest-core/util/hmac'

module RestCore
  # http://tools.ietf.org/html/rfc5849
  class Oauth1Header
    def self.members
      [:request_token_path, :access_token_path, :authorize_path,
       :consumer_key, :consumer_secret,
       :oauth_callback, :oauth_verifier,
       :oauth_token, :oauth_token_secret, :data]
    end
    include Middleware

    def call env, &k
      start_time = Time.now
      headers = {'Authorization' => oauth_header(env)}.
                  merge(env[REQUEST_HEADERS])

      event = Event::WithHeader.new(Time.now - start_time,
                "Authorization: #{headers['Authorization']}")

      app.call(log(env.merge(REQUEST_HEADERS => headers), event), &k)
    end

    def oauth_header env
      oauth = attach_signature(env,
        'oauth_consumer_key'     => consumer_key(env),
        'oauth_signature_method' => 'HMAC-SHA1',
        'oauth_timestamp'        => Time.now.to_i.to_s,
        'oauth_nonce'            => nonce,
        'oauth_version'          => '1.0',
        'oauth_callback'         => oauth_callback(env),
        'oauth_verifier'         => oauth_verifier(env),
        'oauth_token'            => oauth_token(env)).
        map{ |(k, v)| "#{k}=\"#{escape(v)}\"" }.join(', ')

      "OAuth #{oauth}"
    end

    def attach_signature env, oauth_params
      params = reject_blank(oauth_params)
      params.merge('oauth_signature' => signature(env, params))
    end

    def signature env, params
      [Hmac.sha1("#{consumer_secret(env)}&#{oauth_token_secret(env)}",
                 base_string(env, params))].pack('m0')
    end

    def base_string env, oauth_params
      method   = env[REQUEST_METHOD].to_s.upcase
      base_uri = env[REQUEST_PATH]
      payload  = payload_params(env)
      query    = reject_blank(env[REQUEST_QUERY])
      params   = reject_blank(oauth_params.merge(query.merge(payload))).
        to_a.sort.map{ |(k, v)|
          "#{escape(k.to_s)}=#{escape(v.to_s)}"}.join('&')

      "#{method}&#{escape(base_uri)}&#{escape(params)}"
    end

    def nonce
      [OpenSSL::Random.random_bytes(32)].pack('m0').tr("+/=", '')
    end

    # according to OAuth 1.0a spec, only:
    #     Content-Type: application/x-www-form-urlencoded
    # should take payload as a part of the base_string
    def payload_params env
      # if we already specified Content-Type and which is not
      # application/x-www-form-urlencoded, then we should not
      # take payload as a part of the base_string
      if env[REQUEST_HEADERS].kind_of?(Hash)  &&
         env[REQUEST_HEADERS]['Content-Type'] &&
         env[REQUEST_HEADERS]['Content-Type'] !=
           'application/x-www-form-urlencoded'
        {}

      # if it contains any binary data,
      # then it shouldn't be application/x-www-form-urlencoded either
      # the Content-Type header would be handled in our HTTP client
      elsif contain_binary?(env[REQUEST_PAYLOAD])
        {}

      # so the Content-Type header must be application/x-www-form-urlencoded
      else
        reject_blank(env[REQUEST_PAYLOAD])
      end
    end

    def reject_blank params
      params.reject{ |k, v| v.nil? || v == false ||
                                      (v.respond_to?(:strip) &&
                                       v.respond_to?(:empty) &&
                                       v.strip.empty? == true) }
    end
  end
end